Capacitor discharge ignition system with overspeed control

ABSTRACT

Disclosed herein is a capacitor discharge ignition circuit with engine overspeed control comprising an engine ignition subcircuit electrically connected to a capacitor and including a primary winding and a normal nonconductive electronic ignition switch connected in series with the primary winding and including a trigger element operative to close the ignition switch ahd thereby to discharge the capacitor through the ignition subcircuit to effect spark production, together with a speed control sub-circuit connected to the capacitor in parallel with the ignition sub-circuit and including resistor means and a normally nonconductive electronic speed control switch connected in series with the resistor means and including a control element operative to close the speed control switch and thereby to discharge the capacitor through the speed control sub-circuit during a time interval determined by the resistor means and independent of engine rotation, and coil and magnet means rotatable relative to each other in accordance with engine speed and electrically connected to the capacitor, to the control element, and to the trigger element for sequentially charging the capacitor with a speed control charge, generating a speed control pulse and applying the speed control pulse to the control element, charging the capacitor with an ignition charge, and generating a trigger pulse and applying the trigger pulse to the trigger element.

United States Patent [1 1 Anderson et al.

[ Apr. 8, 1975 CAPACITOR DISCHARGE IGNITION SYSTEM WITH OVERSPEEDCONTROL [751 lnventors: Phillip A. Anderson, Waukegan;

Donald H. Wood, Gurnee, both of 111.

[73] Assignee: Outboard Marine Corporation,

Waukegan, Ill.

[22] Filed: Sept. 27, 1973 [21] Appl. No.: 401,344

[52] US Cl. 123/118; 123/148 C [51] Int. Cl. F02p 11/02 [58] Field ofSearch 123/118, 148 S, 148 C, 123/148 E [56] References Cited UNITEDSTATES PATENTS 3.581.720 6/1971 Hemphill 123/118 3,703,889 11/1972 Bodiget al 123/118 X Primary E.\'aminerCharles J. Myhre AssistantE.\'uminerW. Rutledge, Jr. Attorney, Agent, or Firm-Michael, Best &Friedrich [57] ABSTRACT Disclosed herein is a capacitor dischargeignition circuit with engine overspeed control comprising an engineignition sub-circuit electrically connected to a capacitor and includinga primary winding and a normal nonconductive electronic ignition switchconnected in series with the primary winding and including a triggerelement operative to close the ignition switch ahd thereby to dischargethe capacitor through the ignition sub-circuit to effect sparkproduction, together with a speed control sub-circuit connected to thecapacitor in parallel with the ignition sub-circuit and includingresistor means and a normally nonconductive electronic speed controlswitch connected in series with the resistor means and including acontrol element operative to close the speed control switch and therebyto discharge the capacitor through the speed control sub-circuit duringa time interval determined by the resistor means and independent ofengine rotation, and coil and magnet means rotatable relative to eachother in accordance with engine speed and electrically connected to thecapacitor, to the control element, and to the trigger element forsequentially charging the capacitor with a speed control charge,generating a speed control pulse and applying the speed control pulse tothe control element, charging the capacitor with an ignition charge, andgenerating a trigger pulse and applying the trigger pulse to the triggerelement.

9 Claims, 2 Drawing Figures 15 F l l 1 l 76 5/ l l l l a l l 32 77 I l76 1 75 i l 2/ 94 l J0 ------r l l 5l g? I l 1 V06 l i 5 1 L l l. .L

CAPACITOR DISCHARGE IGNITION SYSTEM WITH OVERSPEED CONTROL BACKGROUND OFTHE INVENTION The invention relates generally to capacitor dis chargeignition circuits and, more particularly, to capacitor dischargeignition circuits with engine overspeed control, i.e., to circuits whichdiscontinue ignition operation in the event of attempted engine rotationabove a predetermined speed.

Attention is directed to the following U.S. patents which disclosecapacitor discharge ignition circuits with overspeed control:

Hemphill, U.S. Pat. No. 3,581,720 issued June 1.

I97]; Bodig, U.S. Pat. No. 3,703,889 issued November 28,

SUMMARY OF THE INVENTION The invention provides a capacitor dischargeignition system which prevents ignition operation during engine rotationabove a predetermined speed. Such prevention of ignition operation isprovided incident to increasing speed by reason of the decrease in timeinterval which occurs between successive events caused by enginerotation. More specifically, prior to charging of the capacitor with anignition charge and subsequent triggering of the ignition circuit, thecapacitor is charged with a speed control charge which is subsequentlydischarged through an electronic speed control switch, preferably anormally nonconductive SCR, connected in series with a resistor whichcontrols the time interval of full discharge. Such time interval isessentially independent of engine speed. Because of the use of an SCR,the switch remains on until full discharge. When the time interval(related to engine speed) between the beginning of discharge of thespeed control charge and subsequent charging of the capacitor with anignition charge becomes less than the time interval (independent ofengine speed) for full discharge of the speed control charge through theresistor, subsequent charging of the capacitor with an ignition chargeoccurs when the speed control switch is on. Accordingly, when the engineis rotating above the predetermined speed, the ignition charge will beimmediately disipated through the resistor as the speed control switchis still conducting. However, in the event the engine is rotating belowthe predetermined speed, the speed control switch opens prior to thenext charging of the capacitor with an ignition charge and, accordingly,the ignition charge is available for discharge in the normal manner toproduce a spark.

More specifically, the invention provides a capacitor discharge ignitioncircuit with engine over-speed control comprising an engine ignitionsub-circuit electrically connected to a charge capacitor and including aprimary ignition coil winding and a normally nonconductive electronicignition switch connected in series with the primary winding andincluding a trigger element operative to close the ignition switch andthereby to discharge the capacitor through the ignition subcircuit toeffect spark production, a speed control subcircuit connected to thecapacitor in parallel with the ignition sub-circuit and includingresistor means and a normally nonconductive electronic speed controlswitch connected in series with the resistor means and including acontrol element operative to close the speed control switch and therebyto discharge the capacitor through the speed control sub-circuit duringa time interval determined by the resistor means and independent ofengine rotation, and coil and magnet means rotatable relative to eachother in accordance with engine speed and electrically connected to thecapacitor, to the control element, and to the trigger element forsequentially charging the capacitor with a speed control charge,generating a speed control pulse and applying the speed control pulse tothe control element, charging the capacitor with an ignition charge. andgenerating a trigger pulse and applying the trigger pulse to the triggerelement.

Accordingly, when the engine rotates above a predetermined speed, thetime interval between generation of the speed control pulse and chargingof the capacitor with the ignition charge is less than the time intervalof discharge of the speed control charge from the capacitor through thespeed control sub-circuit, whereby the speed control switch isconductive at the time of charging of the capacitor with the ignitioncharge, and whereby the ignition charge is immediately dischargedthrough the speed control sub-circuit to prevent subsequent discharge ofthe ignition charge through the ignition sub-circuit in response togeneration of the ignition trigger pulse.

One of the principal features of the invention is the provision of acapacitor discharge ignition circuit in which engine ignition isprevented in response to rotation above a predetermined speed because aswitch which would otherwise be closed at slower speeds remains open atthe faster speed to discharge the ignition charge on the capacitor priorto ignition triggering of the capacitor.

Other features of the invention will become known by reference to thefollowing drawings, general description, and claims.

DRAWINGS FIG. 1 is a schematic wiring diagram of an ignition circuit inaccordance with the invention.

FIG. 2 is a schematic illustration of a magnet and coil arrangementprovided in an ignition system including the circuit shown in FIG. 1.

Before explaining the invention in detail, it is to be understood thatthe invention is not limited in its application to the details ofconstruction and arrangement of parts set forth in the following generaldescription or illustrated in the accompanying drawings, since theinvention is capable of other embodiments and of being practiced orcarried out in various ways. Also it is to be understood that thephraseology or terminology employed herein is for the purpose ofdescription and not of limitation.

GENERAL DESCRIPTION Shown in FIG. 1 of the drawings is a capacitordischarge ignition circuit 11 which is adapted to operate a singlecylinder engine (not shown) and which includes means for preventingengine ignition operation above a predetermined engine speed.

The ignition circuit 11 includes a spark plug 13 which is connected tothe secondary winding 15 of an ignition assembly or coil 17 including aprimary winding 11 Also included in the ignition circuit 11 is a chargecapacitor 21 which includes opposed plates 23 and 25,

with the plate 23 grounded at 27 and with the plate connected through aresistor 29 to an ignition kill switch 31 which is grounded at 27 andwhich, when closed, connects the plate 25 to ground 27 so as to preventengine ignition operation.

In accordance with the invention, there is provided coil and magnetmeans rotatable relative to each other in accordance with engine speed,electrically connected to the capacitor, to the control element ofastill to be described normally nonconductive electronic speed controlswitch connected in series with a resistor, and to a trigger element ofa still to be described normally nonconductive electronic ignitionproducing switch, and operable to sequentially charge the capacitor witha speed control charge, generate a speed control pulse and apply thespeed control pulse to the control element, charge the capacitor with anignition charge, and generate a trigger pulse and apply the triggerpulse to the trigger element.

More specifically, the ignition circuit 11 also includes an ignitionsub-circuit 35 connected to the plates 23 and 25 of the capacitor 21 andincluding an electronic ignition switch 37 which is connected in serieswith the primary winding 19 and which includes a trigger element 39. Inthe illustrated construction, the ignition switch 37 comprises anormally nonconductive SCR having an anode 41 connected to the primarywinding 19 which, in turn, is connected to the capacitor plate 23,together with a cathode 43 which is connected to the other capacitorplate 25. The ignition SCR 37 also includes a gate which constitutes thetrigger element 39 and which is operative, upon application of atriggering pulse, to turn on the ignition switch, i.e., to render thetrigger switch conductive.

The ignition circuit 11 also includes means for generating a triggerpulse and applying the trigger pluse to the trigger element 39 totrigger or turn on the ignition SCR. In the illustrated construction,such means comprises a trigger coil 51 connected to the trigger element39 and wound about a core 53 (shown schematically) situated adjacent toa pulse magnet 55 rotating in accordance with engine speed so as toproduce a trigger pulse in the trigger coil 51 once for every rotationof the magnet 55.

In addition, there is provided a diode 61 having an anode 63 connectedto the cathode 43 of the ignition SCR 37 and a cathode 65 connected tothe trigger element 39 of the ignition SCR.

The circuit 11 also includes a capacitor charging subcircuit 71including means for charging the capacitor 21 with an ignition charge ata time prior to generation of the trigger pulse. Accordingly, subsequenttriggering of the ignition switch 37 by the trigger pulse will dischargethe capacitor 21 through the ignition subcircuit 35 to generate a sparkat the plug 13. In the illustrated construction, such means comprises acharge coil 73 which is located adjacent the path of a charge magnet 75rotating in accordance with engine speed. At its ends, the charge coil73 is connected to the capacitor plates 23 and 25. Also provided in thecharging subcircuit 71 is a diode 77 having an anode 79 connected to theend 80 of the charge coil and a cathode 81 connected to the other end 82of the charge coil and to the capacitor plate 23. In addition, there isprovided a second diode 83 which includes an anode 85 connected to theother capacitor plate 25 and a cathode 87 connected to the anode 79 ofthe diode 77 and to the end of the charge coil 73.

In normal operation below the predetermined speed, travel of the chargemagnet 75 past the charge coil 73 effects charging of the capacitor 21and, when a trigger pulse is thereafter generated, such pulse turns onthe ignition SCR 37 to discharge the capacitor 21 through the ignitioncoil 17 and thereby to generate a spark at the plug 13.

In accordance with the invention, means are provided for preventingengine ignition operation as just described in the event of enginerotation above the predetermined speed. In further accordance with theinvention, such overspeed control means comprises an engine overspeedcontrol sub-circuit 91 connected to the capacitor 21 and includingresistor means in the form of a resistor 93 chosen to control the timeinterval of discharge of the speed control charge independently ofengine speed, and a normally open electronic speed control switch 95connected in series with the resistor 93. In the illustratedconstruction, the speed control switch 95 compries an SCR having ananode 97 connected to the resistor 93 which, in turn, is connected tothe capacitor plate 23, and a cathode 99 which is connected to the othercapacitor plate 25. In addition, the speed control SCR 95 also includesa gate 101 which constitutes a control element and which is operative,upon application of a speed control pulse, to turn on the speed controlswitch 95, i.e., to render the speed control switch 95 conductive.

The means for preventing engine ignition operation in the event ofengine rotation above a predetermined speed also includes means forcharging the capacitor 21 with a speed control charge during theinterval between trigger pulse generation and subsequent charging of thecapacitor 21 with an ignition charge in response to travel of the magnet75 past the charge coil 21. In the illustrated construction, such meanscomprises the previously described capacitor charging subcircuit and, inaddition, a second charge magnet 105 which rotates, in accordance withengine speed, past the charge coil 73 so as to charge the capacitor 21with a speed control charge during the interval between capacitordischarge through the ignition sub-circuit and subsequent charging ofthe capacitor 21 with an ignition charge in response to rotation of themagnet 75 past the charge coil 73.

The means for preventing engine ignition operation in the event ofengine rotation above a predetermined speed also includes means forgenerating a speed control pulse and for applying the speed controlpulse to the control element 101 of the speed control switch 95 to closethe speed control switch 95 and thereby prevent engine rotation abovethe predetermined speed during the interval between charging of thecapacitor 21 with a speed control charge by the magnet 105 and chargingof the capacitor 21 with an ignition charge by the magnet 75. Such meanscan comprise a trigger coil connected to the control element 101 andwound about a core situated adjacent to pulse magnet rotating in accordance with engine speed so as to produce a pulse in the trigger coilonce for every rotation of the magnet.

In addition, there is provided a diode 105 having an anode 107 connectedto the cathode 99 of the speed control SCR 95 and a cathode 109connected to the control element or gate 101 of the speed control SCR95.

While the immediately preceding description refers to two trigger coils,the preferred and illustrated construction employs a single trigger coili.e., the coil 51, in connection with the magnet 55 which, in responseto rotation past the core 53 of the single trigger coil 51, producesboth the trigger pulse and the speed control pulse with respect to thecoil 51. In addition, the trigger element 39 and control element 101 areconnected to the opposite ends of the coil 51 and it is preferred thatthe trigger element 39 of the ignition SCR 37 be operative in responseto a pulse of one polarity relative to the coil 51 and that the controlelement 101 of the speed control SCR 95 be operative in response to apulse of the other polarity relative to the coil 51. Further, in thespecifically disclosed construction, the pulse magnet 55 comprises twomagnet members 111 and 113 each having an arcuate extent of slightlyless than 180, with one of the magnet members constituting a north poleand with the other magnet member constituting a south pole.

The resistor 93 included in the speed control subcircuit 91 is chosen soas to obtain capacitor discharge through the resistor 93 and speedcontrol switch 95 during a time interval greater than the time intervalwhich occurs between the beginning of such discharge i.e., the time ofspeed control pulse generation, and subsequent charging of the capacitorwith an ignition charge by the magnet 75. As a result, when the engineis rotating above the predetermined speed in the clockwise direction asseen by the arrow 115 in FIG. 2, the speed control switch 95 is stillconducting at the time of attemped capacitor charging by the magnet 75.Accordingly, such attempted charging results in immediate dissipation ofthe charge through the resistor 93 so that an effective charge on thecapacitor 21 is not available at the time of next trigger pulsegeneration. Thus, engine ignition is discontinued.

Upon decrease in the rate of engine rotation below the predeterminedspeed, the time interval between generation of the speed control pulseand charging of the capacitor 21 with an ignition charge by the magnet75 increases due to the slower rotational speed and becomes greater thanthe time interval of full discharge through the speed controlsub-circuit 91 of the speed control charge applied to the capacitor bythe magnet 105. Thus, during engine operation are speeds belowpredetermined speed, the speed control switch 95 opens after fulldischarge through the speed control sub-circuit 91 of the speed controlcharge and prior to subsequent charging of the capacitor with anignition charge by the magnet 75. Such subsequent charging of thecapacitor 21 with an ignition charge provides an effective charge uponthe capacitor 21 at the time of generation of the trigger pulse.

In the illustrated construction, the magnets 75 and 105 which charge thecapacitor 21 can each be single magnets or can each constitute two ormore adjacent magnets 75A and 758 or 105A and 1058 extending in anarcuate array.

Various of the features of the invention are set forth in the followingclaims.

What is claimed is:

l. In an internal combustion engine, a capacitor discharge ignitioncircuit with engine overspeed control comprising a charge capacitor.

a spark plug,

an ignition coil including a secondary winding electrically connected tosaid spark plug and a primary winding,

an engine ignition sub-circuit electrically connected to said capacitorand including said primary winding and a normally nonconductiveelectronic ignition switch connected in series with said primary windingand including a trigger element operative to close said ignition switchand thereby to discharge said capacitor through said ignition subcircuitto effect spark production,

means connected to said capacitor and including a first charge magnetfor charging said capacitor with an ignition charge prior tospark-producing operation of said ignition sub-circuit, means connectedto said trigger element for generating a trigger pulse after charging ofsaid capacitor with said ignition charge, and for applying said triggerpulse to said trigger element to effect closure of said ignition switch,whereby to effect spark production in response to discharge of saidignition charge from said capacitor through said ignition sub-circuit,and means for preventing spark-producing operation of said ignitionsub-circuit in the event of engine rotation above a predetermined speedcomprising a speed control sub-circuit connected to said capacitor inparallel with said ignition sub-circuit and including resistor means anda normally nonconductive electronic speed control switch connected inseries with said resistor means and including a control elementoperative to close said speed control switch and thereby to dischargesaid capacitor through said speed control sub-circuit, means connectedto said capacitor and including a second charge magnet for charging saidcapacitor with a speed control charge during the interval betweengeneration of speed trigger pulse and charging of said capacitor withsaid ignition charge,

and means connected to said control element for generating a speedcontrol pulse during the interval between charging of said capacitorwith said speed control charge and charging of said capacitor with saidignition charge and for applying said speed control pulse to saidcontrol element to effect closure of said speed control switch whereby,when the engine rotates above the predetermined speed, the time intervalbetween generation of said speed control pulse and charging of saidcapacitor with said ignition charge is less than the time interval ofdischarge of said speed control charge from said capacitor through saidspeed control sub-circuit, whereby said speed control switch isconductive at the time of charging of said capacitor with said ignitioncharge, and whereby said ignition charge is immediately dischargedthrough said speed control sub-circuit to prevent subsequent dischargeof said ignition charge through said ignition sub-circuit in response tothe next generation of said ignition trigger pulse.

2. An ignition circuit in accordance with claim 1 wherein said speedcontrol switch is an SCR.

3. An ignition circuit in accordance with claim 1 wherein said resistormeans includes a resistance operable to control the time interval ofdischarge of said speed control charge through said speed controlsubcircuit.

4. An ignition circuit in accordance with claim 1 wherein said means forgenerating said trigger pulse and said speed control pulse comprise asingle trigger coil including one end connected to said trigger elementand one end connected to said control element.

5. An ignition circuit in accordance with claim 4 wherein said means forgenerating said trigger pulse and said speed control pulse comprise apulse magnet rotating in accordance with engine speed and including anarcuately extending north pole surface and an arcuately extending southpole surface spaced from said north pole surface, the sum of the arcuateextent of said north and south pole surfaces being slightly less than360.

6. An ignition circuit in accordance with claim 1 wherein said means forgenerating said trigger pulse and said speed control pulse comprise apulse magnet which rotates in accordance with engine speed and includesan arcuately extending north pole surface and an arcuately extendingsouth pole surface spaced from said north pole surface, a core locatedadjacent to the path of said surfaces, and a single trigger coil woundon said core and including one end connected to said trigger element andone end connected to said control element, whereby said trigger pulse isof one polarity and said speed control pulse is of the other polarity.

7. An ignition circuit in accordance with claim 1 wherein said means forcharging said capacitor with said speed control charge and with saidignition charge include a charge coil connected to said capacitor andmeans for rectifying the voltage generated in said charge coil inresponse to passage of said charge magnets.

8. A capacitor discharge ignition circuit in accordance with claim 1wherein said means for charging said capacitor with said speed controlcharge and with said ignition charge includes a charge coil connected tosaid capacitor and wherein said means for generating said trigger pulseand said speed control pulse comprise a pulse magnet including a northpole surface and a south pole surface spaced from said north polesurface, and a single trigger coil including one end connected to saidtrigger element and one end connected to said control element, andwherein said first and second charge magnets and said north and southpole surfaces rotate in accordance with engine speed, and wherein saidfirst and second charge magnets, said charge coil, said north and southpole surfaces, and said trigger coil are located relative to each otherso as to successively charge said capacitor with said speed controlcharge, generate said speed control pulse, charge said capacitor withsaid ignition charge, and generate said trigger pulse.

9. In an internal combustion engine, a capacitor discharge ignitioncircuit with engine overspeed control comprising a charge capacitor, aspark plug, an ignition assembly including a secondary windingelectrically connected to said spark plug and a primary winding, anengine ignition sub-circuit electrically connected to said capacitor andincluding said primary winding and a normally nonconductive electronicignition switch connected in series with said primary winding andincluding a trigger element operative to close said ignition switch andthereby to discharge said capacitor through said ignition sub-circuit toeffect spark production, a speed control sub-circuit connected to saidcapacitor in parallel with said ignition sub-circuit and includingresistor means and a normally nonconductive electronic speed controlswitch connected in series with said resistor means and including acontrol element operative to close said speed control switch and therebyto discharge said capacitor through said speed control sub-circuitduring a time interval determined by said resistor means and independentof engine rotation, and coil and magnet means rotatable relative to eachother in accordance with engine speed and electrically connected to saidcapacitor, to said control element, and to said trigger element forsequentially charging said capacitor with a speed control charge,generating a speed control pulse and applying said speed control pulseto said control element, charging said capacitor with an ignitioncharge, and generating a trigger pulse and applying said trigger pulseto said trigger element, whereby, when the engine rotates above apredetermined speed, the time interval between generation of said speedcontrol pulse and charging of said capacitor with said ignition chargeis less than the time interval of discharge of said speed control chargefrom said capacitor through said speed control sub-circuit, whereby saidspeed control switch is conductive at the time of charging of saidcapacitor with said ignition charge, and whereby said ignition charge isimmediately discharged through said speed control sub-circuit to preventsubsequent discharge of said ignition charge through said ignitionsub-circuit in response to generation of said ignition trigger pulse.

1. In an internal combustion engine, a capacitor discharge ignitioncircuit with engine overspeed control comprising a charge capacitor, aspark plug, an ignition coil including a secondary winding electricallyconnected to said spark plug and a primary winding, an engine ignitionsub-circuit electrically connected to said capacitor and including saidprimary winding and a normally nonconductive electronic ignition switchconnected in series with said primary winding and including a triggerelement operative to close said ignition switch and thereby to dischargesaid capacitor through said ignition sub-circuit to effect sparkproduction, means connected to said capacitor and including a firstcharge magnet for charging said capacitor with an ignition charge priorto spark-producing operation of said ignition sub-circuit, meansconnected to said trigger element for generating a trigger pulse aftercharging of said capacitor with said ignition charge, and for applyingsaid trigger pulse to said trigger element to effect closure of saidignition switch, whereby to effect spark production in response todischarge of said ignition charge from said capacitor through saidignition sub-circuit, and means for preventing spark-producing operationof said ignition sub-circuit in the event of engine rotation above apredetermined speed comprising a speed control sub-circuit connected tosaid capacitor in parallel with said ignition sub-circuit and includingresistor means and a normally nonconductive electronic speed controlswitch connected in series with said resistor means and including acontrol element operative to close said speed control switch and therebyto discharge said capacitor through said speed control sub-circuit,means connected to said capacitor and including a second charge magnetfor charging said capacitor with a speed control charge during theinterval between generation of speed trigger pulse and charging of saidcapacitor with said ignition charge, and means connected to said controlelement for generating a speed control pulse during the interval betweencharging of said capacitor with said speed control charge and chargingof said capacitor with said ignition charge and for applying said speedcontrol pulse to said control element to effect closure of said speedcontrol switch whereby, when the engine rotates above the predeterminedspeed, the time interval between generation of said speed control pulseand charging of said capacitor with said ignition charge is less thanthe time interval of discharge of said speed control charge from saidcapacitor through said speed control sub-circuit, whereby said speedcontrol switch is conductive at the time of charging of said capacitorwith said ignition charge, and whereby said ignition charge isimmediately discharged through said speed control sub-circuit to preventsubsequent discharge of said ignition charge through said ignitionsub-circuit in response to the next generation of said ignition triggerpulse.
 2. An ignition circuit in accordance with claim 1 wherein saidspeed control switch is an SCR.
 3. An ignition circuit in accordancewith claim 1 wherein said resistor means includes a resistance operableto control the time interval of discharge of said speed control chargethrough said speed control sub-circuit.
 4. An ignition circuit inaccordance with claim 1 wherein said means for generating said triggerpulse and said speed control pulse comprise a single trigger coilincluding one end connected to said trigger element and one endconnected to said control element.
 5. An ignition circuit in accordancewith claim 4 wherein said means for generating said trigger pulse andsaid speed control pulse comprise a pulse magnet rotating in accordancewith engine speed and including an arcuately extending north polesurface and an arcuately extending south pole surface spaced from saidnorth pole surface, the sum of the arcuate extent of said north andsouth pole surfaces being slightly less than 360.degree..
 6. An ignitioncircuit in accordance with claim 1 wherein said means for generatingsaid trigger pulse and said speed control pulse comprise a pulse magnetwhich rotates in accordance with engine speed and includes an arcuatelyextending north pole surface and an arcuately extending south polesurface spaced from said north pole surface, a core located adjacent tothe path of said surfaces, and a single trigger coil wound on said coreand including one end connected to said trigger element and one endconnected to said control element, whereby said trigger pulse is of onepolarity and said speed control pulse is of the other polarity.
 7. Anignition circuit in accordance with claim 1 wherein said means forcharging said capacitor with said speed control charge and with saidignition charge include a charge coil connected to said capacitor andmeans for rectifying the voltage generated in said charge coil inresponse to passage of said charge magnets.
 8. A capacitor dischargeignition circuit in accordance with claim 1 wherein said means forcharging said capacitor with said speed control charge and with saidignition charge includes a charge coil connected to said capacitor andwherein said means for generating said trigger pulse and said speedcontrol pulse comprise a pulse magnet including a north pole surface anda south pole surface spaced from said north pole surface, and a singletrigger coil including one end connected to said trigger element and oneend connected to said control element, and wherein said first and secondcharge magnets and said north and south pole surfaces rotate inaccordance with engine speed, and wherein said first and second chargemagnets, said charge coil, said north and south pole surfaces, and saidtrigger coil are located relative to each other so as to successivelycharge said capacitor with said speed control charge, generate saidspeed control pulse, charge said capacitor with said ignition charge,and generate said trigger pulse.
 9. In an internal combustion engine, acapacitor discharge ignition circuit with engine overspeed controlcomprising a charge capacitor, a spark plug, an ignition assemblyincluding a secondary winding electrically connected to said spark plugand a primary winding, an engine ignition sub-circuit electricallyconnected to said capacitor and including said primary winding and anormally nonconductive electronic ignition switch connected in serieswith said primary winding and including a trigger element operative toclose said ignition switch and thereby to discharge said capacitorthrough said ignition sub-circuit to effect spark production, a speedcontrol sub-circuit connected to said capacitor in parallel with saidignition sub-circuit and including resistor means and a normallynonconductive electronic speed control switch connected in series withsaid resistor means and including a control element operative to closesaid speed control switch and thereby to discharge said capacitorthrough said speed control sub-circuit during a time interval determinedby said resistor means and independent of engine rotation, and coil andmagnet means rotatable relative to each other in accordance with enginespeed and electrically connected to said capacitor, to said controlelement, and to said trigger element for sequentially charging saidcapacitor with a speed control charge, generating a speed control pulseand applying said speed control pulse to said control element, chargingsaid capacitor with an ignition charge, and generating a trigger pulseand applying said trigger pulse to said trigger element, whereby, whenthe engine rotates above a predetermined speed, the time intervalbetween generation of said speed control pulse and charging of saidcapacitor with said ignition charge is less than the time interval ofdischarge of said speed control charge from said capacitor through saidspeed control sub-circuit, whereby said speed control switch isconductive at the time of charging of said capacitor with said ignitioncharge, and whereby said ignition charge is immediately dischargedthrough said speed control sub-circuit to prevent subsequent dischargeof said ignition charge through said ignition sub-circuit in response togeneration of said ignition trigger pulse.